Raster scan tv#

Circuits in the tv use the вЂњsyncвЂќ pulses to get in step with the transmitted signal. 2-1B.ДЄ television broadcasting station sends a signal to the television that contains special synchronizing pulses. All television sets rely on a technique called вЂњraster scanning.вЂќ In raster scanning the crt beam is deflected in a weaving pattern that sweeps across the screen and down many times per second as shown in Fig. The most popular method for graphics displays today takes advantage of the fact that there are literally hundreds of millions of television sets in the world. Of course you can build a low-cost stroke graphics display using 8-bit dac's but it will never compete with the digitally derived displays. Since the dac contains complex analog circuits that must be trimmed periodically and since it contains temperature dependent components the stroke graphics method is favored only when money is no object. In stroke graphics we need a computer to generate the points that define the shape to send to the display and an expensive digital-to-analog converter (dac) to convert these digital points to voltages for the crt. We call such a display technique stroke graphics because the display is sent voltage point pairs and the beam draws a line in one stroke from the last point to the current point. Like an oscilloscope, the display had an X and Y in- ics because the display is sent voltage point pairs and the beam in the crt to a point proportional to the amplitudes of the input signals.

In the early years of computer graphics the main display device was not a standard television screen but rather an expensive cathode-ray tube (crt) like the kind found in oscilloscopes. STROKE GRAPHICS AND RASTER SCAN: THE OLD AND THE NEW

Raster scan